The present invention relates to a redispersible or soluble product obtainable by freeze drying an aqueous dispersion of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene.
The preparation of polythiophenes and dispersions thereof for use in antistatic coatings has been described in the literature e.g. xe2x80x98Handbook of Organic Conductive Molecules and Polymersxe2x80x99, ed. H. S. Nalwa, J. Wiley and Sons, 1997. Polythiophenes have conductive properties which can be controlled, for example, by the degree of doping.
FR-A-88 7976 discloses a process for the preparation or electrically conducting polymers based on polythiophenes by chemical polymerization of thiophene in a reaction medium comprising a ferric salt, an alkyl halide and water.
U.S. Pat. No. 5,254,648 discloses a process for the preparation of electrically conductive, doped polythiophene, the process comprising: unsubstituted thiophene, a ferric salt which is effective as a doping agent and as an agent inducing polymerization and which is added to the reaction medium as an anhydrous ferric salt, an alkyl halide present in an amount of less than 0.04 liter per gram thiophene, and water, wherein the water is introduced in an amount ranging between 0.009 and 900% by weight of the alkyl halide, and wherein the water and the anhydrous ferric salt are present in a molar ratio ranging between 0.01 and 6.
WO A-99 25753 describes a method for the preparation of polyanilines, polythiophenes and polypyrroles. EP-A 0 440 957 discloses dispersions of polythiophenes, constructed from structural units of formula (I): 
in which R1 and R2 independently of one another represent hydrogen or a C1-4-alkyl group or together form an optionally substituted C1-4-alkylene residue, in the presence of polyanions.
EP-A-0 686 662 discloses mixtures of A) neutral polythiophenes with the repeating structural unit of formula (I), 
in which R1 and R2 independently of one another represent hydrogen or a C1-4-alkyl group or together represent an optionally substituted C1-4-alkylene residue, preferably an optionally with alkyl group substituted methylene, an optionally with C1-12-alkyl or phenyl group substituted 1,2-ethylene residue or a 1,2-cyclohexene residue, and B) a di- or polyhydroxy- and/or carboxy groups or amide or lactam group containing organic compound; and conductive coatings therefrom which are tempered to increase their resistance preferably to  less than 300 ohm/square.
EP-A 1 081 549 discloses a coating composition comprising a solution of a substituted or unsubstituted thiophene-containing-conductive polymer, a film-forming binder; and an organic solvent media; the media having a water content of less than 37 weight percent. Percentages by weight of poly(3,4-ethylenedioxythiophene) of 0.1% in the coating solution are exemplified.
EP-A 1 081 546 discloses a coating composition of an electrically-conductive polymer (ECP) and an organic solvent media wherein the solvents are selected from the group consisting of alcohols, ketones, cycloalkanes, arenes, esters, glycol ethers and their mixtures; the media having a water content of less than 12 weight percent. Percentages by weight of ECP of 0.02 to 0.18% in the coating solution are exemplified.
EP-A 1 081 548 discloses a coating composition comprising a substituted or unsubstituted thiophene-containing electrically-conductive polymer and an organic solvent media; the media having a water content of less than 12 weight percent. Percentages by weight of poly(3,4-ethylenedioxythiophene) of 0.02 to 0.1% in the coating dispersion are exemplified.
In large scale methods for preparing aqueous dispersions of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene the solids content is limited to only a few percent, due to production reasons such as the need for ultrafiltration, the viscosity of the dispersion etc. It should be noted that such dispersions are often erroneously referred to, even in patent texts, as solutions due to their very small particle size, 20 to 50 nm, of the polythiophene/polyanion latex. Shipment of such dilute dispersions is expensive and cumbersome in view of the high volume and weight associated therewith.
Freeze drying has been developed as a method of preserving and increasing the transportability, e.g. in space travel, expeditions and military campaigns, of perishable organic materials such as food, flavours, aroma""s, blood products and pharmaceutical formulations. Since the 1960""s it has been applied to upwards of 400 foods from meat to fruits and vegetables. This background is reflected in a definition of freeze drying (or lyophilization process) given by T. A. Jennings and H. Duan in 1995 in the Journal of Parenteral Science and Technology, volume 49, no. 6 pp. 272-282, as xe2x80x98a stabilising process in which a substance is first frozen and then the quantity of solvent is reduced, first by sublimation and then by desorption to values that will no longer support biological activity or chemical reactionsxe2x80x99.
It is an object of the present invention to provide a highly concentrated latex of a substituted or unsubstituted polythiophene.
A further aspect of the present invention is the provision of a method of making an antistatic or electroconductive layer.
A still further aspect of the present invention is the provision of a coating solution or dispersion of a latex from a highly concentrated dispersion latex of a polythiophene.
Another aspect of the present invention is the provision of a printing ink from a highly concentrated dispersion latex of a polythiophene.
Further objects and advantages of the present invention will become apparent from the description hereinafter.
Efforts aimed at obtaining concentrated products from a dispersion or solution of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene provides solids or films using conventional techniques such as evaporating aqueous dispersions or precipitation produced compositions have shown that, if redispersible in water or organic solvents, redispersion required considerable investment of time and thermal and/or mechanical energy.
Surprisingly it has been found that if freeze-drying, an unconventional concentration technique, is applied to an aqueous dispersion of a latex comprising a polyanion and a copolymer or polymer of a substituted or unsubstituted thiophene, a sponge-like or wool-like powder is produced, which can be rapidly redispersed or dissolved without expenditure of thermal and/or mechanical energy in water or an organic solvent so as to obtain a coating dispersion or solution (optionally adding other ingredients) without leaving a coarse fraction behind. The resulting coating dispersion or solution can be applied to any object, for example a support.
A redispersible or soluble product is provided by the present invention obtainable by freeze drying an aqueous dispersion of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene.
A method for making an antistatic or electroconductive layer or pattern is further provided by the present invention comprising the steps of redispersing or diluting the above-mentioned product by adding water or an organic solvent so as to obtain a solution or dispersion; optionally adding other ingredients to the solution or dispersion; andxe2x80x94applying the solution or dispersion to an object.
A coating solution or dispersion is also provided according to the present invention comprising the above-mentioned redispersible or soluble product.
Use of the above-mentioned coating solution or dispersion is also provided by the present invention for preparing an antistatic or electroconductive layer.
A printing ink is also provided according to the present invention comprising the above-mentioned redispersible or soluble product.
Use of the above-mentioned printing ink is also provided by the present invention for preparing an antistatic or electroconductive layer.
Freeze drying according to the present invention is a lyophilization process in which a substance is first frozen and then the quantity of solvent (generally water) is reduced, first by sublimation (=primary drying process) and then by desorption (=secondary drying process) until the temperature of the shelves becomes equal to the atmospheric temperature in the freeze dryer. The freeze-drying process is enabled by the ability of solid materials such as ice to sublime (change directly into a gas without passing through a liquid phase) under the right conditions.
The term xe2x80x9cdry productxe2x80x9d according to the present invention means dry to touch and is associated with no apparent liquid phase.
The term xe2x80x9cprinting inkxe2x80x9d according to the present invention means an ink capable of being applied in a printing process e.g. in flexographic printing, offset printing, driographic printing, inkjet printing, (silk) screen printing.
The term layer according to the present invention means a continuous coating.
The term pattern according to the present invention means a discontinuous coating.
The term xe2x80x9caqueousxe2x80x9d as used herein shall be understood as defining dispersions wherein the liquid phase consists of water or water/solvent mixtures provided that the water content is higher by volume than the solvent content.
The electric resistivity of a layer is generally expressed in terms of surface resistivity RS (unit xcexa9; often specified as xcexa9/square). Alternatively, the electroconductivity may be expressed in terms of volume resistivity RV=RSxc2x7d, wherein d is the thickness of the layer, volume conductivity kV=1/RV [unit: S(iemens)/cm] or surface conductivity kS=1/RS [unit: S(iemens).square].
The term xe2x80x98electroconductivexe2x80x99 according to the present invention means having a surface resistivity below 106 xcexa9/square. 106 xcexa9/square is typically regarded as a value of surface resistivity which distinguishes electroconductive materials from antistatic materials. Antistatic materials typically have a surface resistivity in the range from 106 to 1011 xcexa9/square and are not suitable as an electrode.
Conductivity enhancement refers to a process in which contact with high boiling point liquids such as di- or polyhydroxy- and/or carboxy groups or amide or lactam group containing organic compound optionally followed by heating at elevated temperature, preferably between 100 and 250xc2x0 C., during preferably 1 to 90 seconds, results in conductivity increase. Alternatively, in the case of aprotic compounds with a dielectric constant xe2x89xa715, e.g. N-methyl-pyrrolidinone, temperatures below 100xc2x0 C. can be used. Such conductivity enhancement is observed with polythiophenes and can take place during the preparation of a layer or subsequently. Particularly preferred liquids for such treatment are N-methyl-pyrrolidinone and diethylene glycol such as disclosed in EP-A 686 662 and EP-A 1 003 179.
According to the present invention a redispersible or soluble product obtainable by freeze drying an aqueous dispersion of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene is provided.
The first step in freeze-drying a product is to convert it into a frozen state. During the freezing process, the solvent (water) is preferably crystallized. The formation of ice crystals results in a separation of the solutes and the solvent. Then the ice crystals are removed by sublimation under vacuum conditions. While the sublimation or primary drying process removes most of the water from the frozen matrix, there can still be greater than 5% moisture weight/weight with respect to the freeze-dried product in the cake.
Thereafter the remaining water is removed by desorption. It has been found that the water content of the freeze-dried product, according to the present invention, has a strong effect on the redispersibility thereof. The products are highly hygroscopic. For example, the weight of PEDOT/PSS obtained by drying a 1.2% by weight aqueous dispersion at 102xc2x0 C. increased by 16 to 23% at room temperature, whereas the weight increase in an exicator was only 8%. Products freeze-dried at room temperature, according to the present invention, typically have a water content of 15 to 20% by weight. Further drying of the freeze-dried product in a vacuum drying cupboard at 110xc2x0 C. and a drying cupboard at 110xc2x0 C. results in products, which are more difficult to disperse.
According to a first embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the redispersible or soluble product is a dry, spongy, woolly powder, a concentrated dispersion or a paste. A concentrated dispersion or a paste can be obtained instead of a powder by incomplete freeze-drying of the aqueous dispersion. The redispersible or soluble product as a powder, concentrated dispersion or paste can be dissolved or redispersed by adding water, organic solvent or mixtures of water/solvent optionally with other ingredients such as surfactants and dispersants.
According to a second embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the concentrated dispersion or paste has a solids content higher than 10% by weight.
According to a third embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the concentrated dispersion or paste has a solids content higher than 20% by weight.
According to a fourth embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the concentrated dispersion or paste has a solids content higher than 50% by weight.
A concentrated dispersion in an organic solvent such as diethylene glycol or N-methyl-pyrrolidinone, can, for example, be realized by freeze drying a mixture of the organic solvent and the aqueous dispersion or solution of polythiophene/polyanion to a dispersion of polythiophene/polyanion in the organic solvent.
This concentrated dispersion or paste can be diluted or redispersed to obtain any desired concentration in a similar manner to the powder.
According to a fifth embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the substituted thiophene is substituted in at least one of the 3- or 4-positions substituted with a substituent selected from the group consisting of alkoxy, substituted alkoxy, alkyl, substituted alkyl, aryl and substituted aryl groups or the 3- and 4-positions are linked with an optionally substituted oxy-alkylene-oxy group.
According to a sixth embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the polymer of a substituted thiophene is represented by formula (I): 
in which n is larger than 1 and each of R1 and R2 independently represents hydrogen or an optionally substituted C1-4 alkyl group or together represent an optionally substituted C1-4 alkylene group or an optionally substituted cycloalkylene group, preferably an ethylene group, an optionally alkyl-substituted methylene group, an optionally C1-12 alkyl- or phenyl-substituted ethylene group, a 1,3-propylene group or a 1,2-cyclohexylene group.
According to a seventh embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the polymer or copolymer of a substituted thiophene is a polymer or copolymer of a (3,4-dialkoxy-thiophene) in which the two alkoxy groups together represent an optionally substituted oxy-alkylene-oxy bridge selected from the group consisting of: (3,4-methylenedioxy-thiophene), (3,4-methylenedioxythiophene) derivatives, (3,4-ethylenedioxythiophene), (3,4-ethylene-dioxythiophene) derivatives, (3,4-propylenedioxythiophene), (3,4-propylenedioxythiophene) derivatives, (3,4-butylene-dioxythiophene) and (3,4-butylenedioxy-thiophene) derivatives and copolymers therewith.
According to a eighth embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the polymer or copolymer of a substituted thiophene is a polymer or copolymer of a (3,4-dialkoxy-thiophene) in which the two alkoxy groups together represent an oxy-alkylene-oxy bridge substituted with a substituent selected from the group consisting of alkyl, alkoxy, alkyloxyalkyl, carboxy, alkylsulfonato and carboxy ester groups.
According to a ninth embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the polymer of a substituted thiophene is a poly(3,4-dialkoxy-thiophene) in which the two alkoxy groups together represent an optionally substituted oxy-alkylene-oxy bridge which is a 1,2-ethylene group, an optionally alkyl-substituted methylene group, an optionally C1-12 alkyl- or phenyl-substituted 1,2-ethylene group, a 1,3-propylene group or a 1,2-cyclohexylene group.
Such polymers are disclosed in Handbook of Oligo- and Polythiophenes Edited by D. Fichou, Wiley-VCH, Weinheim (1999); by L. Groenendaal et al. in Advanced Materials, volume 12, pages 481-494 (2000); L. J. Kloeppner et al. in Polymer Preprints, volume 40(2), page 792 (1999); P. Schottland et al. in Synthetic Metals, volume 101, pages 7-8 (1999); and D. M. Welsh et al. in Polymer Preprints, volume 38(2), page 320 (1997).
The preparation of such a polythiophene and of aqueous dispersions containing such a polyanion and a polymer or copolymer of a substituted thiophene is described in EP-A-440 957 and corresponding U.S. Pat. No. 5,300,575. Basically the preparation of polythiophene proceeds in the presence of polymeric polyanion compounds by oxidative polymerisation of 3,4-dialkoxythiophenes or 3,4-alkylenedioxythiophenes according to formula (II): 
wherein R1 and R2 are as defined for formula (I).
Stable aqueous dispersions of a polymer or a copolymer of a substituted or unsubstituted thiophene can be obtained by dissolving thiophenes, e.g. those corresponding to formula (II), a polyacid and an oxidising agent in water, optionally containing an organic solvent, optionally containing a comonomer, and then stirring the resulting solution or emulsion at 0xc2x0 C. to 100xc2x0 C. until the polymerisation reaction is completed. The polymer or copolymer of a substituted or unsubstituted thiophene formed by the oxidative polymerisation is positively charged, the location and number of such positive charges being not determinable with certainty and therefore not mentioned in the general formula of the repeating units of the polymer or copolymer of a substituted or unsubstituted thiophene.
Suitable oxidising agents are those that are typically used for the oxidative polymerisation of aromatic monomers such as pyrrole, thiophene and aniline. Preferred oxidising agents are iron (III) salts, e.g. FeCl3, Fe(ClO4)3 and the iron (III) salts of organic acids and inorganic acids containing organic residues or combinations thereof. Other suitable oxidising agents are H2O2, K2Cr2O7, alkali or ammonium persulfates, alkali perborates, potassium permanganate and copper salts such as copper tetrafluoroborate. Air or oxygen can also be used as oxidising agents. Theoretically, 2.25 equivalents of oxidising agent per mol of thiophene are required for the oxidative polymerisation thereof (J. Polym. Sci. Part A, Polymer Chemistry, Vol. 26, p.1287, 1988). In practice, however, the oxidising agent is used in excess, for example, in excess of 0.1 to 2 equivalents per mol of thiophene.
The polyanions of the redispersible or soluble product obtainable by freeze drying according to the present invention are disclosed in EP-A 440 957 and are formed from polyacids or can be added as a salt of the corresponding polyacids, e.g. an alkali salt.
According to a tenth embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the polyanion is the anion of a polymeric carboxylic acids, such as poly(acrylic acid), poly(methacrylic acid) and poly(maleic acid), or of a polymeric sulphonic acid, such as poly(styrene sulphonic acid) or poly(vinyl sulphonic acid). These polycarboxylic acids and polysulphonic acids can also be copolymers of vinylcarboxylic acids and vinylsulphonic acids with other polymerizable monomers, e.g. acrylic acid esters, methacrylic acid esters and styrene.
According to an eleventh embodiment of the redispersible or soluble product obtainable by freeze drying according to the present invention, the polyanion is the anion of poly(styrene sulphonic acid) or of copolymers thereof with styrene.
The molecular weight of these polyanion forming polyacids is preferably between 1000 and 2xc3x97106, more preferably between 2000 and 5xc3x97105. These polyacids or their alkali salts are commercially available and can be prepared according to the known methods, e.g. as described in Houben-Weyl, Methoden der Organische Chemie, Bd. E20 Makromolekulare Stoffe, Teil 2, (1987), pp. 1141.
A coating solution or dispersion is realized according to the present invention comprising a redispersible or soluble product, which may be a powder, paste or concentrated dispersion, obtainable by freeze drying an aqueous dispersion of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene.
According to a first embodiment of the coating solution or dispersion according to the present invention, the coating solution or dispersion further comprises water or an organic solvent.
According to a second embodiment of the coating solution or dispersion according to the present invention, the coating solution or dispersion has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 2% by weight of the coating solution or dispersion.
According to a third embodiment of the coating solution or dispersion according to the present invention, the coating solution or dispersion has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 5% by weight of the coating solution or dispersion.
According to a fourth embodiment of the coating solution or dispersion according to the present invention, the coating solution or dispersion has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 10% by weight of the coating solution or dispersion.
According to a fifth embodiment of the coating solution or dispersion according to the present invention, the coating solution or dispersion has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 1% by weight of the coating solution or dispersion and a water content of less than 12% by weight of the coating solution or dispersion.
According to a sixth embodiment of the coating solution or dispersion according to the present invention, the coating solution or dispersion has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 1% by weight of the coating solution or dispersion and a water content of less than 6% by weight of the coating solution or dispersion.
According to a seventh embodiment of the coating solution or dispersion according to the present invention, the coating solution or dispersion can be used for preparing an antistatic or electroconductive layer.
The coating solution or dispersion may comprise additional ingredients, such as a hardening agent e.g. an epoxysilane, such as 3-glycidyloxypropyl-triethoxy-silane, as described in EP-A 564 911, which is especially suitable when coating on a glass substrate; one or more surfactants; spacing particles; adhesion promoting agents, UV-filters or IR-absorbers.
A printing ink is realized according to the present invention comprising a redispersible or soluble product, which may be a powder, paste or concentrated dispersion, obtainable by freeze drying an aqueous dispersion of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene.
According to a first embodiment of the printing ink according to the present invention further comprising water or an organic solvent.
According to a second embodiment of the printing ink according to the present invention, the printing ink has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 2% by weight of the printing ink.
According to a third embodiment of the printing ink according to the present invention, the printing ink has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 5% by weight of the printing ink.
According to a fourth embodiment of the printing ink according to the present invention, the printing ink has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 10% by weight of the printing ink.
According to a fifth embodiment of the printing ink according to the present invention, the printing ink has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 1% by weight of the printing ink and a water content of less than 12% by weight of the printing ink.
According to a sixth embodiment of the printing ink according to the present invention, the printing ink has a concentration of the latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene of at least 1% by weight of the printing ink and a water content of less than 6% by weight of the printing ink.
The printing ink may comprise additional ingredients, such as one or more binders, a hardening agent e.g. an epoxysilane, such as 3-glycidoxypropyltrimethoxysilane, as described in EP-A 564 911, which is especially suitable when coating on a glass substrate; one or more surfactants; one or more dispersants; spacing particles; adhesion promoting agents, UV-filters or IR-absorbers. Suitable polymer binders are described in EP-A 564 911.
Lithographic inks have viscosities of about 15 Pa.s to 35 Pa.s depending upon the ink formulation, drying mechanism, printing machine and speed of printing. Gravure and flexographic inks vary greatly, but a typical press-ink viscosity is about 15 mPa.s. Typical viscosities of screen printing inks are about 2 Pa.s. Inkjet inks vary in viscosity from about 2 mPa.s to 20 mPa.s depending upon the type of inkjet process, nozzle construction, printing speed, ink-drying mechanism and print quality required. Hot-melt inkjet inks are solid at room temperature and are normally printed at about 150xc2x0 C., when their viscosity is of the order of 40 mPa.s.
Non-transparent printing inks can be realized by additionally incorporating a pigment such as LEVACRYL(copyright) A-SF, a black pigment from BAYER, in a weight sufficient to give non-transparency in the layer thickness being coated.
Layers of the printing inks exhibit excellent adhesion to phosphor layers, polyacrylate subbing layers, polycarbonate and polyesters e.g. poly(ethene terephthalate) with surface resistances xe2x89xa61000 xcexa9/square at visual light transmissions  greater than 75%, with xe2x89xa785% being obtainable.
According to a twelfth embodiment of the redispersible or soluble product obtainable by freeze drying, according to the present invention, the product further comprises a binder.
According to a thirteenth embodiment of the redispersible or soluble product according to the present invention, the product further comprises a binder having a glass transition temperature above 25xc2x0 C.
According to an eighth embodiment of the coating solution or dispersion according to the present invention, the coating solution or dispersion further comprises a binder or a thickener.
According to a seventh embodiment of the printing ink according to the present invention, the printing ink further comprises a binder or thickener.
Suitable binders for use in the present invention are described in EP-A 564 911, which is hereby incorporated by reference, and include water-soluble polymers, such as poly(vinyl alcohol), water-soluble homo- and co-polymers of acrylic acid and homo- and co-polymers of methacrylic acid, and polymer latexes.
Suitable thickeners are polyacrylates and polysaccharides. Preferred polyacrylate thickeners are high molecular weight homo- and copolymers of acrylic acid crosslinked with a polyalkenyl polyether such as the CARBOPOL(copyright) resins of B. F. Goodrich with CARBOPOL(copyright) ETD-2623 being particularly preferred. Preferred polysaccharide thickeners include cellulose, cellulose derivatives e.g. carboxymethyl cellulose, silica, guar gum and xanthan gum, with xanthan gum being particularly preferred e.g. BIOSAN(copyright) S from Hercules Inc., USA and Kelzan(copyright) T from MERCK and Co., Kelco Division, USA.
Particularly preferred binders and thickeners for use in the redispersible or soluble product, coating solution, coating dispersion or printing ink, according to the present invention, are:
POLYVIOL(trademark) WX48 20=a poly(vinyl alcohol) from WACKER CHEMIE
CARBOPOL(trademark) ETD2623=an acrylic acid copolymer crosslinked with a polyalkenyl polyether from B. F. Goodrich;
CERIDUST(trademark) 130=a polyethylene wax from Hoechst;
JONREZ(trademark) SM700=a rosin based resin from Johnson Polymer;
JONREZ(trademark) SM705=a rosin based resin from Johnson Polymer;
JONREZ(trademark) SM729=a rosin based resin from Johnson Polymer;
KLUCEL(trademark) H=a hydroxypropylcellulose from Hercules Inc.;
NEOCRYL(trademark) BT24=an alkaline-soluble acrylic copolymer from Zenica Resins
Preferred water-soluble binders include poly(vinyl alcohol) and homo- and co-polymers of hydroxyethyl methacrylate and copolymers of 2-propenoic acid 2-phosphonooxy)ethyl ester and copolymers of 2-methyl-2-propenoic acid 2-phosphonooxy)ethyl ester. Preferred polymer latexes are homo- or co-polymers of a monomer selected from the group consisting of styrene, acrylates, methacrylates and dienes e.g. isoprene and butadiene. Particularly preferred polymer latexes for use in the redispersible or soluble product, coating solution, coating dispersion or printing ink, according to the present invention, are:
LATEX01=poly(methyl methacrylate) latex with a particle size of 90 nm, available as a 20% by weight aqueous dispersion;
LATEX02=copolyester latex of 26,5 mol % terephthalic acid, 20 mol % isophthalic acid, 3.5 mol % sulfo-isophthalic acid and 50 mol % ethylene glycol, available as a 20% by weight aqueous dispersion;
LATEX03=vinylidene chloride, methyl methacrylate, itaconic acid (88/10/2) terpolymer, available as 30% by weight aqueous dispersion;
LATEX04=a copolymer of 80% ethyl acrylate and 20% methacrylic acid, available as a 27% by weight aqueous dispersion;
LATEX05=a copolymer of 49% methyl methacrylate, 49% of butadiene and 2% itaconic acid, available as a 30% by weight aqueous dispersion;
LATEX06=a poly(ethyl acrylate), available as a 30% by weight aqueous dispersion.
LATEX03, LATEX04, LATEX05 and LATEX06 all have glass transition temperatures below 25xc2x0 C. Such binders may be treated with a hardening agent, e.g. an epoxysilane such as 3-glycidyloxypropyltrimethoxysilane as described in EP-A 564 911, which is especially suitable when coating on a glass substrate.
According to a fourteenth embodiment of the redispersible or soluble product obtainable by freeze drying, according to the present invention, the product further comprises a surfactant.
According to a ninth embodiment of the coating solution or dispersion according to the present invention, the coating solution or dispersion further comprises a surfactant.
According to an eighth embodiment of the printing ink according to the present invention, the printing ink further comprises a surfactant.
Anionic and non-ionic surfactants are preferred. Suitable surfactants for use in the redispersible or soluble product, redispersible or soluble product, coating solution, coating dispersion or printing ink, according to the present invention, are:
Surfactant No 01=perfluoro-octanoic acid ammonium salt, available as a 30% solution;
Surfactant No 02=MARLON(trademark) A365, supplied as a 65% concentrate of a sodium alkyl-phenylsulfonate by Hxc3x9cLS;
Surfactant No 03=AKYPO(trademark) OP80, supplied as an 80% concentrate of an octyl-phenyl-oxy-polyethyleneglycol(EO 8)acetic acid by CHEMY;
Surfactant No 04=ARKOPAL(trademark) N060 (previously HOSTAPAL(trademark) W), a nonylphenylpolyethylene-glycol from HOECHST;
Surfactant No 05=ZONYL(trademark) FSO 100, a block copolymer of polyethyleneglycol and polytetrafluoroethene with the structure: F(CF2CF2)yCH2CH2O(CH2CH2O)xH, where x=0 to ca. 15 and y=1 to ca. 7 from DUPONT, supplied as a 5 wt. % solution;
Surfactant No 06=HOSTAPAL(trademark) B, a sodium trisalkylphenyl-polyethyleneglycol(EO 7-8)sulphate from HOECHST, supplied as a 50% concentrate;
Surfactant No 07=ARKOPON(trademark) T, a sodium salt of N-methyl-N-2-sulfoethyl-oleylamide from HOECHST, supplied as a 40% concentrate;
Surfactant No 08 MERSOLAT(trademark) H76, a sodium pentadecylsulfonate from BAYER, supplied as a 76% concentrate;
Surfactant No 09=SURFINOL(trademark) 485, an ethoxylated acetylenic diol surfactant from Air Products.
According to a fifteenth embodiment of the redispersible or soluble product obtainable by freeze drying, according to the present invention, the product further comprises a conductivity enhancing agent.
According to a tenth embodiment of the coating solution or dispersion, according to the present invention, the coating solution or dispersion further comprises a conductivity enhancing agent.
According to a ninth embodiment of the printing ink according to the present invention, the coating solution or dispersion further comprises a conductivity enhancing agent.
Suitable conductivity enhancing agents are linear, branched or cyclic aliphatic C2-20 hydrocarbon or an optionally substituted aromatic C6-14 hydrocarbon or a pyran or a furan, said organic compound comprising at least two hydroxy groups or at least one xe2x80x94COX or xe2x80x94CONYZ group, wherein X denotes xe2x80x94OH and Y and Z independently of one another represent H or alkyl; or a heterocyclic compound containing at least one lactam group.
Examples of such organic compounds for use in the redispersible or soluble product, coating solution, coating dispersion or printing ink, according to the present invention, are e.g. N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidone, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylurea, formamide, dimethylformamide, and N,N-dimethylacetamide. Preferred examples are sugar or sugar derivatives such as arabinose, saccharose, glucose, fructose and lactose, or di- or polyalcohols such as sorbitol, xylitol, mannitol, mannose, galactose, sorbose, gluconic acid, ethylene glycol, di- or tri(ethylene glycol), 1,1,1-trimethylol-propane, 1,3-propanediol, 1,5-pentanediol, 1,2,3-propanetriol, 1,2,4-butanetriol, 1,2,6-hexanetriol, or aromatic di- or polyalcohols such as resorcinol.
Particularly preferred conductivity enhancing agents for use in the coating solution or dispersion or printing ink according to the present invention are: N-methyl-pyrrolidinone and diethylene glycol.
Suitable supports for use in the method of the present invention are polymeric films such as poly(ethylene terephthalate), poly(ethylene naphthalate), polystyrene, polyethersulphone, polycarbonate, polyacrylate, polyamide, polyimides, cellulosetriacetate, polyolefines, polyvinylchloride, etc. Also inorganic substrates can be used such as silicon, ceramics, oxides, glass, polymeric film reinforced glass, glass/plastic laminates.
The redispersible or soluble product obtainable by freeze drying an aqueous dispersion of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene, according to the present invention, can be used in various applications. The dispersions or solutions, printing ink and coated layers obtained therefrom can be used for making electrodes that can be used in various electrical or semiconductor devices.
Preferred applications for the electroconductive layers prepared with dispersions are photovoltaic cells, electroluminescent devices such as organic or inorganic light-emitting diodes, and displays, especially flat panel displays such as LCDs.
The resistivity of the electroconductive layer comprising a polythiophene prepared according to the present invention is sufficiently low to be used as electrode in a device that draws or generates a small current, such as a solar cell. However, devices that may draw a higher current, such as LEDs, may require an electrode wherein the organic electroconductive layer is combined with another layer having a better conductivity, e.g. an ITO layer. Other embodiments are disclosed in EP-A 1 013 413 and EP-A 0 554 588.
While the present invention will hereinafter be described in connection with preferred embodiments thereof, it will be understood that it is not intended to limit the invention to those embodiments. The ingredients used in the EXAMPLES and not mentioned above are summarized below:
ECCOCOAT(trademark) CC-2=a conductive polymer from Emerson and Cumming Speciality Polymers
Z6040=3-glycidoxypropyltrimethoxysilane from Dow Corning.
The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.